The present invention is a process of optically resoluting one optical isomer from the mixture of a platinum complex compound consisting of dextrorotatory and levorotatory optical isomers.
A platinum complex compound of Formula (1) is known as raw material of a carcinostatic agent, and the compound of Formula (1) is obtained by reacting potassium haloplatinate [K.sub.2 Pt(II)X.sub.4 ] (X is chlorine, bromine or iodine) and 1,2-cyclohaxanediamine to produce a compound of Formula (2), to an aqueous solution of which is added two equivalences of a silver nitrate solution to precipitate and filter off the chlorine, the bromine or the iodine in the Formula (2) as silver chloride, silver bromide or silver iodide, respectively, and adding to the filtrate thereof an organic dibasic acid for cyclization. ##STR1## However, the compound of Formula (1) produced by this process is generally the mixture of a dextrorotatory substance (d-isomer) and a levorotatory substance (1-isomer). Generally, however, only one of the dextrorotatory substance and the levorotatory substance of the platinum complex compound is effective as a carcinostatic agent or the like. While, for example, only the dextrorotatory substance of the platinum compound of Formula (1) possesses the function as a carcinostatic agent, the levorotatory substance possesses toxicity to the contrary.
Even if a dextrorotatory dihalogen complex compound of Formula (2) is employed as starting material in order to obtain only the dextrorotatory compound of Formula (2), the retention of the optical isomerism is not guaranteed so that an optical isomer of 100% purity cannot be obtained in most cases. It is desirable, however, to optically resolute the dextrorotatory substance and the levorotatory substance at nearly 100% efficiency when high optical purity is required in such a case of the raw material of a carcinostatic agent.
Further, a process of accurately determining the optical purity of a platinum compound produced has not existed. The purity of the conventional mixture of a dextrorotatory substance and a levorotatory substance has only been indirectly estimated by means of its angle of rotation or circular duchroism. The industrial value of the compound of Formula (1) as the raw material of a carcinostatic agent remarkably increases if the purity of a desired platinum complex compound is exactly calculated.